From a practical point of view, the first three Apollo missions were
primarily engineering test flights. Exploration and science were of
secondary importance and, indeed, the Lunar Modules which were flown on
those missions simply couldn't carry much equipment. The LM had been
designed as the sparest vehicle capable of completing a landing
mission; and it had always been a struggle to find room in the weight
budget for scientific equipment and exploration gear. Confidence in
the spacecraft - coupled with incremental improvements in performance -
permitted slight increases in the amount of useful cargo that could be
landed on the Moon but, from a practical point of view, Apollo 14 was
about the most sophisticated mission that could have been accomplished
with the original Apollo hardware.

Of course, NASA and the space community as a whole had always wanted a
good deal more from a mission than what a pair of walking astronauts
could accomplish during a thirty-hour stay. As mentioned previously,
in the early fifties rocketeer Wernher von Braun, astronomer Fred
Whipple, and science writer Willy Ley published a series of articles in
Collier's Magazine in which they described a hypothetical lunar landing
mission on a far grander scale. They expected that a crew of fifty
lunar explorers would journey to the Moon in three large landers
assembled and fueled in earth orbit. Two of the landers would be able
to make the round trip to the Moon and back and, on the outbound leg,
would each carry a crew of twenty. The third lander would be the cargo
ship, carrying a crew of ten and, in place of fuel for the trip home,
about 300 tons of cargo. Von Braun and the others imagined that the
expedition would stay on the Moon for six weeks, arriving just after
local dawn, staying through that two-week day and the following night,
and departing just before sunset on their second lunar day. Rather
than live in ships, the explorers would, after unloading the cargo,
disassemble the cargo hold and use the resulting half-cylinder sections
as Quonset huts - one for living quarters and the other for labs. Of
course, there was a great deal of material to be moved and von Braun
and the others provided the expedition with cranes - one on each ship -
and with three ten-ton tractor-trailers. Once the base was
established, the tractor-trailers could be put to use as exploration
vehicles, first for trips in the immediate vicinity of the base and
then, just before dawn on the second day, for a 300-kilometer
cross-country trek to a large crater where, it was hoped, evidence
would be found to prove once-and-for-all whether large lunar craters
were formed by impacts or by volcanic action.

(In reality, high-quality photos taken with such instruments as the
Palomar telescope on Earth and the Lunar Orbiter spacecraft provided
enough data that, for the majority of planetary scientists, the
question had been answered - generally in favor of impact origins for
the vast majority of features - long before Apollo 11. Readers
interested in a more complete discussion would do well to consult Don
Wilhelm's "To a Rocky Moon". However, as Jack Schmitt
remarked during our review of this Apollo 15 summary, even for the
majority who were convinced that almost all lunar craters were impact
structures, "there were a few features we said might be volcanic
caldera craters, primarily because they were even more strikingly
polygonal than the impact craters. But even the large impact craters
end up with polygonal outlines. It's determined by whatever fracture
system you have and, in the case of Meteor Crater (Arizona), the
fracture systems are northwest and northeast trending and you just get
better excavation along those fractures and you end up with a square
crater. On the Moon, it looks like it's a hexagonal fracture pattern
that predominates and you end up with hexagons. There are some sharply
polygonal craters. But, when you look at their rims in cross section,
they're delta-shaped instead of ramp shaped. So I said that there's a
good possibility that those are calderas rather than impact craters.
We've never been to one so we don't know. I gave a paper on Copernicus
once, and I think that abstract has more on that. But those are a
minor percentage of the large craters.")

Von Braun's imagined lunar expedition was probably grander than
anything that was really possible for a first mission. However, if
global politics had not forced the early pace and sequence of space
exploration and we had built up capabilities and facilities in Earth
orbit before mounting the first lunar expeditions, perhaps we would
have gone to the Moon with the intent of establishing a permanent base
camp. Indeed, even within the constraints of Apollo, NASA would have
liked nothing better than to design and build an unmanned,
cargo-version of the LM to support long visits and, eventually, a
modest lunar base; but, in the late 60s, with budgets shrinking and
dreams being put on hold, all that was really possible was to upgrade
the LM design so that crews could land in more heavily-ladened versions
which would let them stay a little longer and range farther afield.

Of course, NASA had no way of knowing until quite late in the game
just how quickly the first landing would be achieved. Most of the
people of Apollo had all they could handle in just getting the first
generation hardware designed, built, and tested. Consequently, the
agency didn't give serious thought to upgrades or to advanced missions
until the first-generation designs were ready for test. Only in
September 1967 was NASA ready to put some thought into an upgraded LM
which would carry - as it turned out - nearly a ton of extra equipment
and supplies. Because productivity could only be increased if the
astronauts stayed longer on the Moon, supplies of food, water, oxygen,
and power would take up much of the increased allotment. However,
because exploration and geologic survey work were expected to be the
main focus of the three-day J missions, there were also discussions
about taking along an electric-powered car. However, preliminary
estimates suggested that there would only be room in the cargo budget
for a Rover weighing about 225 kilograms; and it wasn't clear - at
least during the Christmas season of 1967 when the first memos were
being written - that a reliable, useful vehicle of so low a weight
could be built.

According to historian Mitchell Sharpe, the notion of an wheeled,
electric-powered lunar exploration vehicle made its first literary
appearance virtually at the dawn of the Automotive Age. In 1901,
almost as soon as it became plausible to think about driving on the
Moon, a Polish writer by the name of Jerszy Zulawski described an early
ancestor of the Lunar Rover. Like all those who would follow in his
footsteps, Zulawski realized that combustion engines wouldn't be
practical on the airless Moon and, rather, chose to power his vehicle
with an electric motor. Like most later concepts of lunar rovers -
including von Braun's ten-ton tractor-trailer - Zulawski's was a big
vehicle with an enclosed cabin. His, he said, could carry a crew of
five and a year's worth of supplies.

For about a half century or so, lunar cars made episodic literary
appearances and then, in the years following World War II, they
received occasional attention from members of the spaceflight
fraternity who were beginning to think seriously about what might be
done on the Moon once von Braun's V-2 weapon grew into a real space
launcher. Most importantly, people started to think about some of the
engineering details - about vehicle weight, power supplies, and
traction on various types of surfaces. Naturally, it took real money
to move the vehicles out of the conceptual stage and it wasn't until
the early, heady days of Apollo - when Congress gave NASA all but a
blank check - that the first design contracts were let. There was no
immediate need for a rover but, with an eye toward an eventual lunar
base, it seemed prudent to make a small investment. The design process
might take several years and, in the beginning, progress could be made
by teams spending sums as small as a couple of hundred thousand
dollars. (For comparison, the whole of Apollo cost about
$24,000,000,000 in the dollars of the time.) A number of contractors
(Boeing, Grumman, Bendix, and others) even invested some of their own
research money in the interest of having a competitive advantage when
NASA decided that it really did want to fly a rover. The culmination
of these early efforts was a concept called MOLAB (Mobile Laboratory):
a two-man, three-ton, closed-cabin vehicle with a range of about 100
kilometers. In 1964, the Marshall Space Flight Center awarded design
contracts to both Boeing and Bendix and, in 1966, both companies built
1/6th-weight prototypes which, early the following year, were put
through field trials in the desert near Yuma, Arizona and scientific
trials near Flagstaff. However, it was becoming obvious that a lunar
base was very far in the future and that there would be no need for so
large a vehicle. After the trials, the MOLAB concept was mothballed
but, not surprisingly, NASA turned first to Boeing and Bendix - with
General Motors as an additional partner- when it came time to define a
lightweight rover for the J missions.

Before proceeding with a discussion of the development of the Apollo
Lunar Rover, Dave Scott - the Apollo 15 Commander - urged me to
include a story that Jack Schmitt told me about lunar flyers.

"There was a major academic - as well as industrial - competition
between the proponents of flyers and rovers. Elbert King at JSC was
the in-house proponent of lunar flyers. Geochemists tended to like
lunar flyers because they didn't worry to much about the geology that
connects individual sample sites. And, those of us who are used to
doing field work tended to like the rover because you were in closer
contact with the ground, even though you couldn't go as far away from
the landing site. Also, from an astronaut perspective, although some
of the astronauts sort of liked the idea of having a flyer, I was
concerned that you would have a very difficult time in training. We
were right in the middle of trying to use the LLTV (Lunar Landing Test
Vehicle) and having all sorts of trouble with that. (Three of four
LLTV's crashed during training and testing before the end of Apollo).
And, here was something smaller that you had to design a trainer for
before you went to the Moon. It just didn't seem to make a lot of
sense to me. And the issue was finally decided at a conference in
Santa Barbara. I don't remember why we had the conference, but Max
Faget was there, of all people. (Faget was an almost legendary
engineer who headed Houston's Engineering and Development Directorate
and who played a major role in the design of the Mercury and Gemini
capsule and the Apollo Command Module). And Max finally said, 'You
know, when you finally start to design this, people are going to come
up with all sorts of good ideas about how to make it safer. And
they'll be good ideas. And it'll grow (in weight) to the point that
you can't use it.' And that statement, from Max Faget, killed the
Flyer. You just never heard of it again. As soon as these proponent
figured out Max Faget didn't want the flyer, they figured out there
wasn't much point in proceeding any further."

The decision to proceed with a lightweight Rover wasn't made until May
23, 1969, the day that the crew of Apollo 10 left lunar orbit for the
trip home. With the first landing now imminent, NASA had hopes of
flying the first of the J-missions within a couple of years and,
clearly, the Rover would have to be designed and built on a tight
schedule. Preliminary design requests had been issued the previous
November (1968) ; final design specifications were released on July 11;
and, on October 28, a contract was awarded to Boeing. It was a
cost-plus-fixed-fee contract initially valued at $19 million and NASA
wanted the first of the flight-ready Rovers delivered by April 1971.
Seventeen months wasn't much time and, as it turned out, meeting the
deadline meant a lot of extra people working a lot of overtime. The
total cost of the project eventually rose to nearly $40 million. In a
time of shrinking NASA budgets and some fairly widespread
disillusionment with Apollo, the cost overrun generated far more press
coverage than was warranted by the relatively small size of the Rover
program. Some members of the public - not to mention a few Congressmen
- didn't understand how three golf carts could cost 40 million dollars.
The answer, of course, is that the major automobile manufacturers
regularly spent far greater sums developing new model passenger cars
and, if only three copies of a new car were ever built, they would be
very pricey, too. When the time came, the Rovers performed beautifully
and proved to be worth every dollar that NASA had spent.

The Boeing Lunar Rover was a far cry from the ten-ton, closed-cabin,
seven-passenger tractor/trailer of the Collier's articles, but it was a
nifty little machine nonetheless. Empty, it weighed in at a spare 209
kilograms (460 pounds) and could be folded up and stored (for the trip
out from Earth) like an intricate toy. As Dave Scott points out,
"the volume into which it could be folded was one of its most
significant features," and that volume can be thought of as a
sandwich 1 1/2 meters (5 feet) on a side and 1/2 meter (20 inches)
thick. One it was deployed on the Moon, it was 3 meters long and 1 1/2
wide, with the tops of the twin seatbacks about 1 1/2 meters off the
ground. When fully loaded with two astronauts and all their gear, it
weighed a hefty 700 kilograms (1500 pounds). It rode on four
wire-mesh wheels and, when fully loaded, had a ground clearance of
about 35 centimeters (14 inches). It had four-wheel, all-electric
drive with a 1/4-horsepower motor turning each of the wheels. Steering
could be done with either the front pair of wheels, the back pair, or
with both pairs; and, at low speed, the Rover could be turned on a
radius equal to its own three-meter length. Between the seats and
slightly forward of the astronauts, there was a small instrument panel
containing displays of, among other things, the Rover's speed and also
a range and bearing to the last place where the crew had initialized
the navigation system - always a place within sight of the LM.

For control, there was a simple T-shaped hand-controller located
between the seats so that, if necessary, the Rover could be operated by
either member of the crew. Naturally, none of the three J-mission
Commanders ever relinquished control - nor did any of the LMP's breach
etiquette by asking to drive. The Rover was capable of 10 to 12
kilometers per hour (6 to 8 miles per hour) on smooth, hard, level
ground. By most terrestrial standards, of course, 12 kph is hardly a
breath-taking speed; but, on the rough, heavily-cratered lunar surface,
hazards could and did appear with exhilarating frequency. If nothing
else, it was a very bouncy ride.

Although the Rover had been designed, primarily, to give the
astronauts mobility and range, it also served as a scientific platform.
Each of the Rovers carried a color-TV camera which could be operated
remotely from Houston. Because of the high information content of the
TV signal, broadcasts were only possible when Rover's high-gain antenna
was pointed almost directly at Earth and, generally, the camera were
only operated when the Rover was parked. Once a crew reached one of
their work stations, they only needed a few seconds to point the
antenna and then could go about their work while Ed Fendell
("Captain Video"), the camera operator on Earth, used zoom
and pan features either to follow the astronauts as they worked or to
supplement crew observations by using the TV to scan the countryside.
And, finally, there was also plenty of room on the Rover for
photographic cameras, film magazines, tools, sample bags, and, on
Apollo 17, a small receiving station for one of the scientific
experiments.

The honor of driving the first Rover on the Moon was supposed to have
been John Young's; and, indeed, it was he and Apollo 16 crewmate
Charlie Duke who participated in preliminary design discussions with
engineers from Boeing and NASA's Marshall Spaceflight Center in January
1970. At the time, the Apollo 13 accident was still a few months in
the future and NASA had, as yet, only formally announced the selection
of one other crew: Shepard, Roosa, and Mitchell for Apollo 14.
Nonetheless, Young and Duke, along with the Command Module Pilot Jack
Swigert, were then serving as the Apollo 13 back-up crew and, in the
normal scheme of crew rotation, were in line for Apollo 16. At the
time, it was expected that their flight would be the first of the J
missions.

Young and Duke liked what they heard and saw. Boeing had come up with
a safe, simple design and the astronauts had only a few substantive
suggestions. First, Boeing had given the Rover a pistol-grip control
just like the ones the astronauts used to fly the LM and the Command
Module. However, Young and Duke pointed out that, on the Rover, they
would be wearing bulky gloves and wanted something that would be easier
to hold. The pistol grip was replaced with a T-handle. Second, in the
interest of providing navigation information so that the astronauts
could figure out just where they were, Boeing was proposing a rather
complex device which, like a missile guidance system, would provide the
astronauts with map coordinates. Given plenty of time and money for
development and testing, Boeing might well have produced such a device,
but the astronauts were quick to point out that all they really needed
was a readout of the direction and distance back to the LM. As it
turned out, development of the navigation system still took a lot of
time and was a major contributor to the cost overrun; but, eventually,
it proved its worth. Not only could the astronauts get back to the LM
"on instruments", but, much more importantly, during the
traverses they could use the navigation readouts to help them find
particular geology stops.

Through the summer of 1970, Young and Duke and a few other astronauts
participated in trials of various Rover prototypes. However, in
September, budget cuts forced the cancellation of what was to have been
a second handcart mission and the crew that was to have flown it - Dave
Scott and Jim Irwin - inherited the first of the Rovers. In November,
when Boeing delivered the first training version of the Rover, it was
Scott who assumed the controls and, in the rough, volcanic country near
Flagstaff, put it through its paces.

Dave Scott was a member of the third group of pilots selected to be
astronauts. He was the first member of his group to reach space when
he flew with Armstrong on Gemini 8; and was the first of the group to
fly a second time when he flew as Command Module Pilot with McDivitt
and Schweickart on Apollo 9. He then secured a firm place in line for
a landing mission when, in April 1969, he was assigned as Commander of
the Backup Crew for Apollo 12. By then, a pattern of crew assignments
had clearly emerged. A backup crew could expect to skip two missions
and then get the next prime-crew assignment; and there was every
expectation that Scott and Irwin and their Command Module Pilot Al
Worden would, in due course, be given Apollo 15. When the assignment
was finally announced in March of 1970 - Scott says that they knew of
the assignment well before it was announced - Scott and Irwin found
themselves in the enviable position of having already gone through most
flight training procedures for Apollo 12. For their own flight, they
still spent plenty of the time in the LM simulators, but they were also
able to devote nearly a third of their training efforts to geology and
other lunar surface activities and, on launch day, were better prepared
to do geology than any crew that yet visited the Moon. And, to top it
off, they were headed for a geologist's paradise.

From a geologic point of view, the Apollo 15 site was of enormous
interest. It had a variety of features to be investigated - and it was
also spectacularly beautiful. Scott and Irwin were scheduled to land
on the fringe of Mare Imbrium (the Sea of Rains), in a small
"bay" surrounded by tall mountains. If, during the Apollo 12
approach, Conrad and Bean thought they were skimming just over the
mountain peaks, then this was the real thing. Indeed, in the seconds
just before pitchover, as Scott flew the Lunar Module Falcon down
through 9000 feet, the summit of 11,000-foot Mount Hadley Delta began
to fill his window forward and left; and, on the other side of the
spacecraft, Irwin could see the summit of Mount Hadley itself, a
round-topped, 14,000-foot peak that dominates the local sky line. And,
to add a final touch of grandeur to the scene, out the left window
Scott could see a long, winding stretch of Hadley Rille, a mile-wide,
V-shaped canyon, that seemed to snake toward him from the southeast.

At pitchover, a scant three minutes before touchdown, Scott got a bit
of a surprise. Like most places on the Moon, the Hadley landing area
is littered with craters but, as it turned out, few are large enough or
deep enough to have early morning shadows. There is nothing that jumps
out at you like the Snowman or Cone Crater. Toward the south edge of
the landing area, virtually at the foot of Hadley Delta, Scott could
see a grouping called the South Cluster and, of course, the rille was
out in front of him. But, out in the middle, a couple of kilometers
NNW of where Scott wanted to set down, landmarks are few and far
between. There are a few moderate-sized craters which, from the
pre-flight analysis, looked as though they would have shadows in them
at landing time; and Scott had spent time in the simulators learning to
recognize them. However, as with the Apollo 14 site , the map and
model makers had missed the subtle undulations that make this a rolling
countryside and make the identification of small craters difficult at
best. Part of the reason was that the Apollo 15 site is well north of
the Moon's equator and the photo coverage didn't have the resolution
that had been available for the earlier sites; and, the net effect was
at, as Scott looked out the window, he couldn't find the patterns he
had hoped to see.

Scott would have liked a clear target but, in truth, Apollo-12-style
precision really didn't matter much for this landing site. Houston had
been watching the tracking data closely and, just before pitchover when
Scott was about 6 kilometers east of the target, Houston warned him
that he was probably about a kilometer south of the planned track. A
quick look at his position relative to the South Cluster and to the
point on the rille where it makes a sharp bend at the foot of Hadley
Delta gave Scott enough information to show him that Houston's call was
a good one. So, he nudged Falcon's line-of-flight toward the north.
Without clear local landmarks, he couldn't be certain of setting down
right on target, but he'd be close enough that the difference wouldn't
matter. He was about the right distance short of the rille (now
trending northwest out in front of him); he was just about due north of
South Cluster; and he was well out into the middle of the desired
landing area. He was certainly within a few hundred meters of the
target and, with the mobility that the Rover would give them, a miss of
a few hundred meters would be a matter of only a few minutes' drive.
The worst that could happen would be that they would spend a few extra
minutes during their initial traverse getting their bearings.

In the hours after landing, prior crews had donned their backpacks and
had gone outside to do an EVA. However, the timing of the launch and a
desire not to thoroughly disrupt their sleep meant that, by the time
they landed, Scott and Irwin had been awake for 11 hours and, if they
had tried to get in a full 8-hour EVA, would have would have put in a
26-hour day before they got into their hammocks. Consequently, they
planned to spend the next several hours working inside the LM and then
to have an eight-hour rest period before going out for the first
time.

To fill out landing day, Scott and Irwin gave the scientists back in
Houston a thorough description of the surrounding countryside. Rather
than restrict themselves to the views out the forward-facing windows,
they donned their helmets and gloves for what was billed as a
"Stand-up EVA". (Scott now wishes that they had called it a
"Site Survey".) Two hours after the landing they were ready.
They bled all the air out of the cabin; and then Scott opened the
overhead hatch. With that done and the docking hardware out of the way
(a daunting task in the tight confines of the LM, Scott stood on the
ascent engine cover with his head and arms outside the spacecraft,
bracing himself in the opening as he took pictures with a 70-mm camera
equipped with a long, 500-millimeter lens. By standing up in the
hatch, Scott had a clear view all the way around the horizon.

The rolling nature of the terrain was, of course, even more evident
than it had been during the approach and, as might be expected from the
lack of deep, fresh craters in the area, in the near field Scott could
see virtually no rocks bigger than a few inches across.
"Trafficability," he said, looked "pretty good".
They might be in for a bouncy Rover ride but, otherwise, it didn't look
like they would have any trouble. In the far field, Scott had a clear
view of the mountains and, as far as he could tell, the slopes were
remarkably smooth. (Silver Spur photo) On Silver Spur, a feature that
looked like a hogback ridge on the eastern flank of Hadley Delta, Scott
saw lineations which he thought might indicate either structure or
layering, but neither there nor elsewhere on the slopes could he see
any large boulders. With no haze to obscure the view, his ability to
pick out detail was limited only by his eyesight and, at the distance
of Hadley Delta, he would have seen boulders bigger than a meter or so
across. Off to the north at a similar distance, he could clearly see
rocks blasted out of the bedrock at 800-meter-diameter Pluton Crater;
but, on the mountains, the slopes were smooth. As Jim Irwin said later
at the start of the first EVA, the Hadley site was a bit reminiscent of
Sun Valley, the spectacular ski resort in the mountains of Idaho; and,
everywhere Scott looked, there were the grey, rounded contours of the
mountains and craters and - as it did for other crews - the mental leap
from lunar dust to snow came easily.

After a half hour of verbal description and photo taking, Scott climbed
down, reinstalled the docking hardware, closed the hatch, and then,
along with Irwin, started doffing his suit. For the first time on an
Apollo mission, the astronauts would sleep in their underwear, free for
a few hours from the damp constriction of the pressure garment. They
were the first of the LM crews to have the chance to get really
comfortable in the LM hammocks.

During the hours when Scott and Irwin were actually asleep, they slept
well that first night. Unfortunately, they didn't get quite as much
sleep as they would have liked, but the shortfall was all in a good
cause. They'd finished up the prior evening's tasks about an hour
late; and then, in the morning, Houston had to wake them up an hour
early to check out a small oxygen leak that was soon traced to an
unclosed cap on the urine disposal line. It was a problem that was
easily fixed and, as Scott told Houston, "the sleeping up here is
really good; and if y'all ever see another little problem like that,
why, we'd only be too happy to roll over and take care of it. I think,
as a matter of fact, we'd even sleep better if we knew that you
wouldn't mind waking us." Despite the late start and the early
wake-up, they got about five hours of apiece and that was a lot more
than any of the prior crews had been able to get.

Preparations for the first real EVA went quickly. Scott and Irwin
discovered that they could chin themselves on some overhead guard rails
and, while they were hanging, stick both feet into the suit. In
one-sixth gravity, it was an almost effortless maneuver and, only four
and a half hours after Houston wake-up, they were out on the lunar
surface. The first order of business was to deploy the Rover. For
this mission, rather than deploy the ALSEP experiments first, Scott and
Irwin were going to take immediate advantage of the Rover and make a
four-kilometer geology trip to the area where the rille abuts the foot
of Hadley Delta. The advantages of the Rover didn't come free of cost,
but the price certainly wasn't high in relation to the return. It only
took them forty-five minutes to unstow and assemble the Rover and
another hour to load it with tools and sample bags.

When he took the Rover out on a brief test drive, Scott was a bit
disconcerted to discover that he didn't have front steering but, after
a few minutes of fiddling with switches, decided to press on. From his
pre-mission training, he knew that he could manage on rear steering
alone and two hours after they started cabin depressurization, he and
Irwin were rolling. The ride was about as bumpy as one might expect in
a rough, roadless land. As Scott described it later in the mission,
much of the terrain is so hummocky that, from the low spots, "you
can hardly see over your eyebrows". Mostly, they drove along at
ten kilometers per hour (10 "klicks"), going in and out of
subdued craters, pitching up and down and rolling from side to side.
At one point, Irwin joked that Scott's driving was making him seasick

"What do you expect," said CapCom Joe Allen," traveling
on the mare!".

In reality, the rolling and pitching motions produced nothing like the
thrills that they got when they occasionally crested a rise and came
upon a crater fresh enough and big enough to give them a heart-stopping
jolt. Often, Scott had no time at all to react and, when they hit, the
Rover turned into a "bucking bronco" with all four wheels
bouncing up off of the ground. Even if Scott did have a little
warning, when he tried to turn hard at any speed above about five
klicks, the rear wheels tended break out and threatened to send the
Rover into a flat spin. They were both very glad to be wearing seat
belts.

The only real problem that Scott and Irwin had with the Rover
concerned the seat belts. Prior to the mission, no one had fully
considered that, in the light lunar gravity, the suits wouldn't
compress very much when the astronauts sat down. Unfortunately, the
belts couldn't be adjusted and the fit was very snug. Indeed, buckling
up proved to be a significant chore, but was absolutely necessary. In
order to complete all of their planned activities, they needed to make
good time. Scott needed to stay as close to maximum speed as he could.
He could minimize the unevenness of the ride by keeping his eyes on
the road, by driving straight through the subtle craters, and by
braking before he attempted any evasive turns; but there was still the
occasional hard bump. Because of the weak lunar gravity, oscillations
in the suspension system damped out more slowly than they would have on
Earth and it was always a bouncy ride. It wasn't a fast drive, but it
certainly was "sporty" and they were both glad to be wearing
belts. Fortunately, there weren't many rocks big enough to bother the
Rover nor, as Scott commented at one point, was there much chance of
running into other traffic.

In principle, the problem of reaching a planned geology station was
straightforward. There were plenty of landmarks on the horizon and,
for the first EVA, the most useful of these was St. George Crater, a
dramatic, two-kilometer wide scar which had been blasted into the flank
of Hadley Delta just above and beyond their destination. The crater
was visible throughout the drive and all that Scott really needed to do
was aim his nose at it. However, he had a natural, pilot's interest in
the performance of the navigation system and, on the outward drive, he
and Irwin attempted to put it to use.

Because the navigation gave them a range and bearing to the LM, the
first order of business in finding a specific spot on the map was to
figure out just where they had landed. Any uncertainty in the LM
location translated directly into an uncertain Rover location. Scott
thought he knew where he'd landed but, as they drove along, Irwin
wasn't having any luck matching craters they passed with ones on the
photomaps. Of course, even if they had known exactly where they had
landed, map reading was difficult because (1) there were few large
and/or distinctive craters close at hand, (2) judging crater size was
inherently difficult, and (3) the maps had been derived from photos of
relatively poor resolution. So it was perhaps not surprising that
Irwin was still figuratively scratching his head when, thirteen minutes
and about a kilometer and a half into the drive, they came - quite
unexpectedly - upon the rille. It was immediately obvious that they
were well north of where they thought they had been. Looking down the
trend of the rille toward the southeast they could see where it bends
sharply to the west; and, on the near rim, they could see their
immediate target, the appropriately named Elbow Crater. Scott's first
thought was that somehow they had been heading too much to the west;
but, for now, the details didn't matter. As soon as they reached
Elbow, the folks in the Backroom (as the Science Support Room was
called) would be able to use the range and bearing at a known place to
sort everything out. In the meantime, Scott and Irwin could see where
they wanted to go and, so, turned south and drove along the edge of the
rille. They reached Elbow Crater about ten minutes later.

During this first EVA, Scott and Irwin planned to spend a bit over an
hour doing geology field work: fifteen minutes or so at Elbow and the
rest up on the hillside near St. George. Although the scientific
community had not yet developed a consistent description of lunar
evolution, it was generally believed that the mountains at Hadley had
been uplifted roughly four billion years ago as a result of the giant
impact that formed the Imbrium Basin. During the first few minutes of
that impact, great blocks of rock at what is now the edge of the basin
were pushed up and out, forming the mountain cores which were then
covered with Imbrium ejecta.

(During our review of this Apollo 15 summary, I asked Jack Schmitt how
much of the South Massif is rotated block and how much is ejecta
covering? "Nobody knows. But probably not a lot, relative to the
height of the mountain. For the big basins, what probably happens is
that you get down to depths where lithostatic forces can compete with
the force of the explosion and you get a lot of lateral motions and you
get multi-ring collapse because of the waves that are set up. If there
were a lot of ejecta covering the mountains, you wouldn't see the
rings. On Orientale, which is our best example of a fresh, multi-ring
basin, you still see...In fact, you see mare formed inside the rings.
Certainly the tops of the mountains have a covering of ejecta. And,
also, I think we know from (Apollo 17) Station 6, that some of the
impact melt will be injected into the fractures that form under the
crater.")

Over the first few hundred million years that followed the Imbrium
impact, the basin filled with lava, apparently a thin sheet at a time.
At any one place, a relatively long time may have passed between
successive filling episodes; but, by three to three-and-a-half billion
years ago, the lavas stopped welling up from the interior and the
mare-forming epoch ended. After that, only the steady rain of
impactors produced any change, creating a five-meter cover of regolith
on top of the lava flows, and adding, as well, to the regolith that had
been forming on the mountain slopes. The Apollo 11 and 12 sites had
yielded representative samples of the basaltic lavas underlying the Sea
of Tranquillity and the Ocean of Storms, respectively; and, at Elbow
Crater, Scott and Irwin expected to find samples of Imbrium basalts.
And then, up on the hillside at St. George, geologists hoped and
expected to find samples of ancient lunar crust which, rather than
having been strongly shocked and altered like the Imbrium ejecta that
Shepard and Mitchell sampled at Frau Mauro, had merely been displaced
upward and outward from the center of Imbrium.

As Scott and Irwin got to work at Elbow, it soon became obvious just
how productive the J-missions were going to be. At this, their first
stop, they were over three kilometers from the LM and, yet, had plenty
of cooling water, oxygen, and time for field work. They had plenty of
tools, sample bags, core tubes, and film; and, most importantly, they
were starting work feeling well rested. For ten minutes or so, they
gathered rocks and soil, describing features that the TV couldn't
capture and taking plenty of photographs. And then it was time to move
on.

"I wish we could sit down and play with these rocks for a
while," Scott said as they loped back to the Rover. "Look at
those things!" Then, like Bean before him, he stopped to admire
the glistening face of a particularly handsome rock. "They're
shiny. Sparkly! Look at all these babies in here. Man!"

"Come on, Dave," said Irwin, playing Conrad's role of time
manager. "There'll be lots of them. Let's get back [to the
Rover]."

But Scott wasn't to be denied. "Can't resist it," he said,
and it was only after he'd collected the rock that he was ready to
"go find something neat in St. George". During training,
Scott had become fascinated with geology and his enthusiasm was not to
be denied.

A short distance beyond Elbow Crater, they began to climb up the flank
of Hadley Delta. They weren't going to go all the way up to the rim of
St. George. That would have required a significant cross-slope drive
and, for the moment, all they needed was a point high enough that they
could be sure of being up off the young, mare materials. As the Rover
began to climb, their speed began to drop. Seven minutes from Elbow
they found what they wanted: a meter-sized boulder sitting on the
hillside about fifty meters above the valley floor.

What Scott and Irwin were looking for were coarse-grained crystalline
rocks called anorthosites which had cooled slowly at depth not long
after the Moon had formed. What they discovered was that the boulder
was a close cousin to the rocks Shepard and Mitchell had brought back
from Frau Mauro. It was a composite, heterogeneous rock called a
breccia which had formed when a jumble of rock and soil fragments was
fused together, probably by the Imbrium impact or by an even earlier,
large impact. Because the first sizable rock they found on the
mountain was a breccia, there was a good chance that breccias would be
common and anorthosites, perhaps, would be rare. But only a complete
set of samples would tell the tale of the mountain and, so, Scott and
Irwin wielded rakes, scoops, cameras and sample bags, hammered a double
section of core tube into the soil, and even turned the boulder over so
that they could obtain samples from beneath it, samples which might
tell just how long the rock had been lying where they found it.

The view from the slopes of Hadley Delta can only be described as
spectacular. Thanks to the Rover-mounted TV camera, Scott and Irwin
could share the view with watchers back on Earth. Off in the distance,
Mount Hadley and the hills west of the rille gave the horizon a
distinctive personality - missing at the earlier landing sites - and
provided visual balance to the winding, sinuous rille which trends
north away from the mountain. Because it was still early morning at
Hadley, the eastern wall of the rille was in shadow. In contrast, the
western wall and, in places, parts of the floor were fully lit.
Because of the relatively low resolution of the TV camera, audience
back on Earth couldn't see all of the detail that the astronauts could
see; but, still, it was beautiful and, everywhere in the bottom on the
rille, the floor was littered with boulders big enough to be seen by
all.

By the time they were done, Scott and Irwin had spent fifty minutes at
St. George. It was, by far, the longest and most productive geology
stop that had yet been performed by an Apollo crew. Well-trained and
well equipped, Scott and Irwin were able to make the most of the
limited time and, as well, had the help of people back in Houston who
could, for the first time, not only hear what they were saying but also
see what they were doing. The geologists on Earth couldn't see
minerals and textures in the rock but they could see how the work was
going and, thereby, offer credible, real-time advice.

As they climbed back on the Rover, Scott and Irwin had three options
for getting back to the LM. When they first reached the St. George
station, CapCom Joe Allen had asked if they could see their outbound
tracks, wondering if they'd be able to do the "Hansel and Gretel
trick" and follow the tracks home. Scott laughed and reported
that he'd already checked at Elbow and had no trouble seeing where the
Rover had disturbed the otherwise pristine lunar surface. On this
first visit to the site, with no other tracks to confuse the picture,
there would be no doubt about finding the LM. And even without tracks,
the surrounding mountains provided enough landmarks that they could
have gotten close enough to the LM to see it. However, everyone was
interested in putting the Rover navigation system to the ultimate test
and, as Scott pulled away from the St. George station, he planned to
drive as straight a line back to the LM as the craters and other
obstacles would let him.

For the first part of the drive, Scott had to drive downhill. That
meant that he had a clear view of the ground ahead of him and,
therefore, a chance to comment on things a bit farther afield. In
particular, he was eyeing the slope off to his left. When he and Irwin
got their first look into the rille, it was quite obvious that the
rille wall below Hadley Delta was covered with fine debris. There
seemed to be few, if any, boulders and Scott thought that it might be a
place where someone could drive down into the rille - if not back out.
From this closer vantage point on the hill side, Scott reported that
the slope still seemed to be smooth and boulder-free, and he told
Houston that "if anybody ever comes back, Joe, and wants to go
down into the rille, have them come talk to us, because there's a good
place to do it here." Perhaps he could have driven out of the
canyon by making a series of switchbacks, but this wasn't the time to
try. Indeed, it wasn't a minute later that he found out just how much
there was to learn. On the way down from the St. George, as he crossed
a slope only a little bit flatter than the one he'd just been eyeing,
he got going a bit too fast, tried to avoid an obstacle, and "did
a 180". Thinking back to Irwin's comment about Sun Valley, Scott
decided that he'd just done the first lunar "christie" - and
said so. It was a longish moment or two before he and Irwin stopped
laughing and got going again.

If there was any residual doubt about the Rover navigation system it
was answered just five minutes out of St. George when Irwin spotted a
reflection off the LM. The spacecraft was dead ahead, a sharp little
gleam on the horizon. It was a comforting sight out in the middle of
the wilderness.

Scott and Irwin got back to the LM at about four hours and twenty
minutes into the EVA and planned to spend the remainder of the EVA
deploying the ALSEP experiments. In all, they planned to be out for a
total of seven hours. However, for unknown reasons, Scott was using
oxygen faster than had been expected and, once he was back at the LM,
Houston suggested that he "do as little unnecessary moving around
as possible". Scott was quick to point out that, for most of the
remaining time, he was supposed to drill three deep holes into the
lunar surface - two for a heat flow experiment and one for a deep core
- and, as everyone knew from training, the drilling promised to be hard
work. Indeed, it was probably the most demanding physical work that
either of them expected to do. Houston would keep a close watch on his
oxygen supply.

In most respects, Scott and Irwin had relatively little trouble with
the ALSEP deployment and, with the exception of the drilling, they
completed the work in about an hour and a half. If things had gone
according to plan, Scott would have spent about a half an hour doing
the drilling, emplacing the heat-flow thermometers, and disassembling
the six deep core sections; but almost nothing about the drilling
seemed to go right. On Apollo 16, Charlie Duke drilled his first
heat-flow hole to the full 2.5 meter depth in one minute flat; and, on
Apollo 17, Gene Cernan drilled his in a bit under three. However, both
Duke and Cernan had the advantage of equipment which had been
extensively modified as a result of what turned out to be a very
frustrating experience for Scott.

At the start, the drilling went well enough but, after getting down 20
or 30 centimeters, Scott reported that the ground was getting
'stiffer" and that his rate of progress was slowing dramatically.
After about five or six minutes of effort, he only had the drill stem
about 170 centimeters into the ground and, as far as he could tell, it
seemed as though he'd run into hard rock. Unbeknownst to Scott or
anyone else, the problem wasn't hard rock but, rather, a fundamental
flaw in the design of the drill-stem flutes. When the drill stem was
turning and cutting, the flutes weren't carrying the cuttings to the
surface but, rather, were getting clogged, thereby binding the stem
tightly in the hole. When Scott said that he didn't think he would be
able to get any deeper, Houston decided that this first heat-flow hole
was deep enough and told him to emplace the probes before moving on to
the second hole. In order to do that, Scott first had to detach the
drill from the stem and, when he tried to turn the drill
counter-clockwise to break the connection, the stem twisted freely in
the hole. He then took hold of the stem with one hand and tried to
turn the drill with the other, but it soon became obvious that the two
were virtually frozen together. Scott struggled for a couple of
minutes before Houston suggested that he get the "wrench" off
the Rover and use it to get a better grip on the drill stem. It took a
minute or so before Scott and Irwin figured out that "wrench"
was the piece of equipment they knew as the "vise" intended
for the separation of core sections. Much to everyone's delight, the
vise did the trick. Scott offered heartfelt congratulations to the
people in the Backroom, obviously glad to have finished this
surprisingly difficult hole. The first hole should have taken no more
than five minutes, but it consumed a quarter hour of precious time.

Any hopes that Scott may have had about the second hole were quickly
dashed. As with the first hole, he managed to get the drill stem down
about 170 centimeters but then no farther. With time running out,
Houston told Scott that they wanted him to abandon the effort, at least
for this EVA, so that he could help Irwin set up one last piece of
ALSEP equipment and then head back to the LM for close-out. Tomorrow,
after they had finished their second traverse and the drill experts had
a chance to think things through, they could give it another try.

By the time they were ready to leave the ALSEP site, Scott and Irwin
were about six hours into the EVA and, because of the status of Scott's
oxygen supply, Houston wanted them back inside the LM in about thirty
minutes more. Scott was eager to make the best use of that time as he
could and suggested that they not bother with the seatbelts for the
short drive back to the LM. He would drive slowly, he promised.
Minutes were precious; and they would gain about three minutes by not
fiddling with the belts and only lose one or so by driving at a slower
speed. Back at the LM, Scott saved a little more time by not turning
the TV on.

In all, these little economies probably saved about five minutes,
which Scott then put to good use at the very end of the EVA. Once he'd
finished all his planned close-out activities and had sent Irwin up the
ladder, Scott asked Houston if there was anything else he might do.
Rarely at a loss for suggestions, Houston was quick to ask that he
erect the solar wind experiment. This was a job that Irwin was
scheduled to do at the start of the second EVA and, indeed, when Scott
reminded Allen that he hadn't handled the equipment since he and Irwin
had finished their Apollo 12 backup training two years before, Houston
backed off the suggestion. However, Scott was not about to waste
precious EVA time by dawdling or by climbing the ladder early. So he
asked Irwin, who was up in the LM getting sample bags out of the way,
if he could look out the right-side window and talk him through the
procedure. Why not get the equipment deployed now, he said, and give
the experimenters lots of data?

"Okay," Irwin told him. "Just take it out about 50
feet."

"Okay. Right about here, huh?"

"Farther, if you want. Yeah. And just pull the tube out full.
Careful when you get to the end, that little thing popped off the
end."

"Okay"

"Just pull it on out."

"Okay."

"And [be] careful, when you rotate the screen, that you rotate in
the right direction, so it doesn't pop off. Just extend the tube
several sections."

Because of the thick gloves, Scott couldn't feel the sections lock,
but he should see red marks come into view at the proper extension.

"Okay. Red. Red. Red. Red," he said. "Okay. That's
easy enough."

Now he had to extend the actual collecting screen like a window
blind.

"And make sure you get the bottom of the screen - not the wire -
over the loop," Irwin told him.

"Okay I see that. The bottom of the screen is over the loop. It
says 'Sun', Scott said, obviously pleased with himself. "I guess
that means that's what you face the Sun, doesn't it?"

"Isn't that a neat experiment?", Irwin asked him.

"Yes, that's the kind of experiment I like. Okay, we're out here
at good distance where it won't get any dust on it from the Rover. And
I'll turn it into the Sun here; stick it in the ground."

After the drilling, it was nice to have a job so simple and
satisfying. The lightweight pole, Scott told Houston, would make a
"good core tube". It went into the ground easily. And with
that he was done.

" Okay, Joe, solar wind is deployed." The five minutes were
gone.

The day hadn't quite gone the way Scott would have preferred. There
had been problems and he and Irwin had been forced to delete planned
activities. What Scott really wanted to do was some geology and some
driving, and the oxygen situation was getting in the way. Was there
anything he could do about the oxygen use, he asked Houston? Was there
a zipper that could use some extra lubrication, just in case there was
a small leak? No, said Houston, it didn't look like a leak. It looked
as though he was burning oxygen at higher than expected rates both
while he was working and while he was driving.

"Okay," he said, "I'll breathe a little less
tomorrow.

But there wasn't a need for anything so extreme, Joe Allen told him.
He and Irwin had just set a bundle of new EVA records: six hours on
the surface and a productive, two-hour, three-kilometer geology trip.
If they managed another couple of EVA's like the first, then nobody was
going to complain.

As Jim Irwin mentioned later in the mission, "the secret of
living up here [in the LM] is getting out of these suits. It really
makes a difference." After a full day's EVA, it was a great
relief to be rid of the constant chaffing and rubbing, free to stretch
arms and legs and flex fingers without constant backpressure from the
suit, and free to let your underwear dry out. Like most things,
freedom from the suit came at a price, and that price was the loss of
elbow room. One-sixth g can be fun and restful but, except when they
were in the hammocks, it was difficult to make much use of the low
gravity within the confines of the LM. The cabin was a place to eat, a
place to repair and prepare equipment with unencumbered fingers, and a
place to sleep.

It was nice to be out of the suit; but, in the morning - rested and
dry - they were eager to get going again. During training, Dave Scott
had developed a real love for geology and the new day promised to be
the sort he could really enjoy. As it turned out, it was one of the
more memorable days of the whole Apollo program.

The need to finish the second heat-flow hole hadn't gone away, nor had
the deep core; but, as had been discussed before Scott and Irwin bedded
down, Houston was willing to defer those tasks to the end of the EVA.
As planned, they would spend the first part of the day driving south
again in the Rover for about four hours of exploration and sampling.
Scott believed that he'd gone to the Moon primarily to take advantage
of the Rover, and the less time the Rover spent parked at the LM or the
ALSEP site, the better he liked it.

By the time Scott and Irwin were out on the surface and were ready to
drive off, it may have seemed as though their luck had turned a bit.
They had been forced to spend a little extra time prior
depressurization cleaning up a few gallons of water that had spilled on
the floor the previous night after a plastic bacteria filter broke off
their water gun; and they'd had to use tape to re-attach Irwin's
backpack antenna which had broken off when he crawled back into the LM
the previous night. But they'd been able to take care of both problems
in short order and now, much to Scott's delight, they found that the
formerly inoperative front steering was now working.

"You know what I bet you did last night, Joe?" said Scott to
his CapCom. "You let some of those Marshall guys come up here and
fix it, didn't you?" Perhaps, he suggested, Boeing had built a
secret launcher so that engineers from Boeing and from Marshall could
come up to the Moon "to fix their Rover".

Three and a half hours after wake-up and an hour after
depressurization, they were rolling. It took Scott a little while to
adapt to the new steering and indeed, after a few minutes, he decided
to stop and switch to front-wheel steering alone. The vehicle, he
said, was much too responsive, especially when he was going downhill.
However, he soon discovered that, with front-wheel steering, the rear
wheels seemed to be drifting rather than centering properly.
Four-wheel steering was better than two, it seemed, and it wasn't going
to take long to adapt.

To start this second trip, Scott drove almost due south toward one of
a handful of medium-sized, fresh craters on the lower slopes of Hadley
Delta. With luck, they might find some of the unaltered samples of the
ancient crust that had eluded them at St. George. The chances of
finding fragments of bedrock depended, of course, on finding a crater
both big enough that the impactor would have penetrated through the
regolith and young enough that the fragments hadn't been re-buried by
the same downhill movement of material that had smoothed the rille
walls below St. George.

As they drove south, the mountain dominated the view. To Scott, it
seemed "as big a mountain as I ever looked up." The lower
slopes averaged about 8 to 10 degrees but, above them, the mountain
sides steepened and rose nearly as far and nearly as fast as the slopes
of Mt. Fuji in Japan. It was a rise of three-and-a-half kilometers in
a horizontal distance of no more than seven, a slope of about 30
degrees. Because most of the mountain is so steep, any material
dislodged by impacts will tend to tumble at least a short distance
downhill and, as Scott and Irwin approached the place where the
mountain and the mare meet, they noticed a clear change in the nature
of the surface. About three hundred meters before they reached the
base of the mountain, they noticed that the number of deep craters was
dropping dramatically and that there seemed to be far fewer small rocks
lying on the surface. Burial by talus that had tumbled down from the
mountain - or by ejecta from impacts on the mountain slopes - seemed
the most likely explanation.

Right at the base of the mountain, Scott and Irwin drove into a
shallow east/west trough, a depression which can be interpreted in at
least two different ways. According to one theory, during the
mare-filling period the cooling lava shrank and pulled slightly away
from the mountain. The resulting gap was then smoothed by impact
erosion and partially filled by material tumbling down off of Hadley
Delta. According to the second theory, the mountain has been subsiding
ever since it was raised in the Imbrium impact and, therefore, the
theory says, the depression marks the bounding
fault, a moat that is
partially filled in as it opens- again - by debris tumbling off the
mountain.

As they had from the LM, Scott and Irwin kept an eye out for fresh
craters and boulders on the hillside but, even as they got closer and
could pick out more detail, there was little more detail to see. Other
than Spur Crater, a fresh, 40-meter feature where they planned to do
most of their sampling, the only striking object that they saw while
driving south from the LM was a large boulder a short way upslope from
Spur. Otherwise, the hillside had the appearance of a dry, sandy,
well-used beach covered with soft hummocks and with poorly-defined,
shallow craters.

The mission plan called for Scott and Irwin to climb the hillside a
bit west of Spur and then turn to the east and make a three-kilometer
drive roughly along a contour line. That would give them a chance to
see what variety of samples were available before making a sampling
stop at the far end of the traverse. They then planned to retrace
their tracks, stopping once about halfway back to Spur and then,
finally, at Spur itself. However, because the drilling wasn't done and
because of Scott's oxygen use rate, time was at a premium and Houston
asked them to think about the relative value of driving versus
sampling. It wasn't very long before Scott and Irwin satisfied
themselves that, except near the few fresh craters already marked on
the map, any one part of the hillside was going to look pretty much
like any other. They had been angling up slope - having passed Spur
Crater on their right - and now were on about the same level as the
boulder and about three hundred meters east of it. There didn't seem
to be much point in driving farther east. It looked as though they
could get representative samples here as well as anywhere else. So,
they parked the Rover and got busy with what proved to be a long and
very productive geology stop.

Working on the hillside took some practice. Without the suits, they
might well have spent much of their time standing sideways to the
slope, with the uphill leg bent a little to keep themselves upright.
However, in the stiff suits it was difficult to stand sideways for very
long and, most of the time, they had to stand facing into the mountain
and leaning into it. As they soon discovered, work on the hillside was
possible only because the soil was soft enough that their boots sank in
a way, giving them extra purchase. In addition, they could sometimes
use a small crater as a step or bench on which to stand . Indeed, they
made life a good deal easier for themselves when, about twenty minutes
into the stop, they moved downslope about 15 meters from the Rover -
and about three meters vertically below it - to a flat-floored,
12-meter crater where they could work without fighting for balance.

After an hour's worth of basically pleasant, rewarding work, Scott and
Irwin were ready to move on. They had collected a large number of
samples, most of them reminiscent of the Frau Mauro breccias. They had
dug a trench, and had taken panoramas and telephoto pictures of Mount
Hadley and of the LM. Scott had even had the novel experience of
getting a core from the rim of the 12-meter crater merely by pushing
the tube with his hand into the soft, loose soil. The only really
difficult part of the experience, they found, was climbing back up to
the Rover. Scott, who has been described to me as a "moose",
bulled his way up the slope while Irwin took his time. When Scott
laughingly said that "I'd sure hate to have to climb up here [from
the base of the hill],", Irwin seconded the thought and suggested
that they "work above the Rover from now on." Fortunately,
once they were back on the Rover, both of them could relax for a few
minutes before they had to climb off and work on the slope again.

As they approached the big boulder a few minutes later, Irwin decided
that, here at least, it might not be such a good idea to park downhill
of the work site. The rock was about a meter high, a meter wide, and
about three meters long and, although it was partially buried and
obviously had been sitting right where it was for millions of years, it
was still easy to imagine the rock sliding down on them or the Rover.
The rock was perched on a slope of about 15 degrees, the steepest
they'd encountered, and prudence seemed in order. Scott parked about
15 meters west and slightly uphill from the boulder, but it wasn't long
before the slope made them think again.

They both had difficulty getting out of the Rover and, once he was on
his feet, Scott had trouble finding a good place to stand as he tried
to point the high gain antenna at Earth. Houston began to wonder if,
once they got down to the boulder, they could get back up to the Rover.
CapCom Joe Allen urged caution.

"Hey, troops", he said, "I'm not sure you should go
downslope very far, if at all, from the Rover."

"No," Scott told him, "it's not far."

The only way to find out if they could make it was to try, but Scott
wanted Irwin to stay with the Rover while he scouted the slope.

Irwin offered encouragement. "I think we can sidestep back
up," he said.

"It's not that hard," said Scott, still edging down toward
the boulder.

Houston was usually cautious about offering advice to the crews but
this was clearly an unusual circumstance and Allen firmly suggested
that Scott try climbing back up before he got too far. Scott agreed
that was a good idea. "Okay; I'm halfway, and I'll go back first.
Why don't you just stay there, Jim?"

"Okay," said Irwin. "Come back up."

"The Rover makes [this slope] feel so easy [to climb]," said
Scott.

"I know it," Irwin said. "[We] should have parked
right beside it."

And that sounded like the best idea. Scott came back up to move the
vehicle. Irwin decided that it would be easier for him to walk down to
the new parking place rather than try to climb into his seat. Because
of the stiffness of the suit, getting on board meant standing at the
side of the Rover and jumping sideways into the seat and, on this
slope, that wasn't going to be easy. Irwin had been watching Scott
carefully and was confident that he could get downhill without trouble.
Once Scott had gotten himself on the Rover, Irwin started down but,
before he'd moved more than a few steps, Scott told him to stop. It
was going to be easiest for Scott to put the Rover in reverse gear and
back up for a few feet before he turned downhill and he wanted Irwin to
watch and wait until he had the Rover securely parked again.

Slowly, Scott turned downslope, first headed west and then looping
east below Irwin's position. He drove along the hillside a bit further
until he was past the boulder, still above it slightly, and then turned
down the hill again to complete an S-shaped path. He parked the Rover
just a bit below the rock and to the east.

Scott still wasn't too sure that they'd be able to work around the
boulder. The Rover was perched so precariously that the left-rear wheel
was a good six inches off the ground and Scott decided that it wouldn't
be prudent to leave the vehicle, just in case it decided to roll
downhill on its own. He suggested that they abandon the effort.

No matter what they did next, Irwin had to pass the boulder on way
down, so he stopped to take a picture. Then he noticed that the
boulder seemed to be light-green in color and offered to come down and
hold the Rover so that Scott could go up to take a look. A green rock
was novel enough that Irwin wanted to make sure that the better
geologist of the pair had a good look at it. Scott agreed instantly.
Irwin climbed down and, once Scott was sure that Irwin was standing
comfortably and had a firm hold on the Rover, he climbed up.

The boulder was green, all right, and a breccia as well. Scott
grabbed a few fragments which, once they were examined back on Earth,
proved to be full of iron-rich and magnesium-rich glass which produced
the green tint. Scott also collected some of the surrounding soil
which, as Irwin had noticed, also had a greenish cast. For about six
minutes, Scott worked around the rock and then, gingerly, made his way
back to the Rover. The slope made the work strenuous and, in
hindsight, not much of scientific value would have been lost if they
had abandoned the boulder. As it turned out, they found similar rocks
once they got downhill at Spur. However, from an operational point of
view, it was useful to know that, with some care taken in parking the
Rover, it would be possible for crews to work on slopes at least as
steep; and, indeed, the Apollo 17 crew spent most of their third EVA
working on steeper slopes.

As he reparked the Rover, Scott had taken care to point it downhill,
in hopes that it would make getting on easier. Irwin suggested that
Scott get on first while he kept his grip on the Rover. Scott made it
on the first try but suggested that Irwin wait where he was until Scott
had driven downhill a short ways to a small crater where he could get
the Rover level enough that Irwin could jump on easily. Irwin even
said that he'd be willing to walk the whole 300 meters down to Spur,
but Scott vetoed the idea and, indeed, with the Rover level, Irwin had
no trouble. For a second time, the crew of Apollo 15 proved the
operational value of small craters.

Spur Crater is big enough that the north (downslope) rim provided a
big, nearly-level parking pad and the work at this stop was relatively
easy. It was also very rewarding.

One of the first things that Scott and Irwin noticed was that they
were standing on more of the greenish soil. Irwin began to wonder if
the greenish appearance might not be due to their dark visors. What if
they got the rocks home and they weren't green after all? The ribbing
would be merciless.

"I've got to admit it really looks green to me, too, Jim, but I
can't believe it's green," said Scott.

"Oh, it's a good story," said Irwin, laughing.
"Something about green cheese? Who would ever believe
it?".

Independently, Scott and Irwin decided to try the obvious experiment
and raised their visors. As their eyes adjusted to the brighter light,
the greenish tint faded a bit but, as Scott said, it was definitely
"a different shade of gray." Two soil samples went into bags
- samples that still had a greenish cast when they were examined after
the mission - and then the astronauts turned their attention to other
matters.

About fifteen minutes into the stop, as they were scanning the rim to
make sure that they were getting a full suite of samples, Irwin spotted
a four-inch rock that glinted in the Sun, sitting up by itself on a
pedestal of breccia. It seemed to beckon, Irwin thought, and to say
"come and sample me." As they looked more closely, there was
no doubt about what they had found. Here was a crystalline rock made
up almost entirely of the mineral plagioclase; and it was very
different in character from the breccias and mare basalts that they had
collected so far.

"I think we found what we came for," Irwin told Houston.

"I think we might have (found) ourselves something close to
anorthosite," Scott said with some satisfaction, "because its
crystalline, and...it's just almost all plag(ioclase). What a
beaut."

Back on Earth, while Scott and Irwin were carefully bagging what came
to be known as the Genesis Rock, commentators lost no time in trying to
come to grips with the significance of the find. Once the great Moon
Race had been won, America's interest in Apollo had declined fairly
quickly and, by this time, all that was left in the public mind was a
question of the Moon's early history. The Apollo 11 and 12 crews had
brought back the mare samples with which geochemists dated the great
lava floods that made the mare; and the 14 crew had brought back the
breccia samples which confirmed general impressions about the age and
composition of the ejecta from the large basins like Imbrium. What
remained to be found was a pristine fragment of the ancient crust and,
in laymen's shorthand, this became the search for the "oldest
rock." In some ways, the "oldest rock" took on
characteristics of the Holy Grail and the Rosette Stone and its
discovery was seen by many as the final Apollo task. There would be
two more flights to fill in a bit of the detail; but, in the public
mind, the quest was now over. Fortunately, NASA had no plans for Scott
and Irwin to rush home if they did find an "oldest rock".
One anorthositic rock from one site could not tell the whole story. As
it turned out, even the Genesis Rock had been shocked at least twice in
the four billion years or so since it slowly solidified deep within the
lunar crust and, at the Apollo 17 landing site, Cernan and Schmitt
found an even older fragment of the Moon. Still, the Genesis Rock was
an important piece of the puzzle and Scott and Irwin were well pleased
with themselves. They had spent time during training learning to
"sort the unusual from the usual," as Dave Scott later said;
and, in particular, had learned how to recognize anorthosite. They had
been primed to look for it; and, after only three hours in the field,
they found some.

During their stop at Spur, Scott and Irwin actually collected four
pieces of anorthosite, with the Genesis Rock being the first and
largest. Along with other tool, the astronauts had a large rake which
looked and worked like a clam rake. Here at Spur, Irwin dragged it
through the soil several times, trapping rock fragments of walnut size
and bigger in the basket and letting the soil and smaller fragments
flow out between the tines. In one two-foot-long swath, he got a
remarkable total of 15 fragments - a real "jackpot" as Joe
Allen called it - and his total collection proved to include not only
three more pieces of anorthosite but also samples of breccia, some
fragments of basalt which had probably been tossed up to Spur from the
mare below, and also some "exotic" fragments thrown onto the
site from even farther away.

The stop at Spur was one of the highlights of the entire Apollo
program and, during the trip back to the LM, Scott and Irwin got a
momentary fright when, during a hurried stop at the South Cluster,
Scott noticed that Irwin didn't have a sample collection bag on his
backpack. Convinced that Irwin's bag had dropped off somewhere back
along the track, Scott quickly reassured himself that he'd been careful
to put the collection bag with the "good rocks" under the
Rover seat before they left Spur.

"Oh, well, win a few lose a few," he said.

There was certainly no time to go back and look for a dropped bag,
even though the Rover tracks would show exactly where they had been.
And, as it turned out, Scott was mistaken about the "lost"
bag. As they were preparing to mount the Rover once more, Scott
remembered that he hadn't bothered to put a fresh bag on Irwin's back
before they left Spur.

"Boy, you had me worried," said Irwin.

"I had me worried too. I knew [I hadn't lost] the one with the
good rocks because I stuck that in the seat pan. But I thought I had
put [a new] one on you, and now I remember I started to put it on you,
and your harness looked loose, so I stuck it on the [back of the Rover]
where it's got a lock. So we're okay."

And then Joe Allen offered a bit of apology. "And we knew all
the time, Dave," he told them. "We should have told you.
Wanted to keep you honest though."

The drive back to the LM was uneventful and, indeed, was a nice break
in an otherwise busy and productive day. There were plenty of
descriptions to pass along to Houston - descriptions of the samples, of
their impressions of the sites, and of Mount Hadley out beyond the LM,
but it was hardly physical work.

"Gee, it's nice to sit down, isn't it?," Scott prompted
Irwin.

"Oh, it is."

"It's a good deal," Scott said, laughingly. "You hop
off and work like mad for 10 minutes and hop back on, sit down, and
take a break." It was a great way to do lunar geology, especially
with more drilling awaiting them back at the LM.

From time to time during the drive, Scott and Irwin could see the LM
out in front of them. From their station at Spur - about 60 meters
above the spacecraft and, of course, nearly five kilometers to the
south - they could see sunlight glinting off of it and were pleased to
note that, with the nose of the Rover pointed at the LM, the bearing
and heading indicators agreed precisely. Neither of them felt
comfortable judging distance yet. Without familiar objects to help
them - trees, telephone poles, houses, and the like - it was almost
impossible to judge sizes and distances and, during the drive home,
Scott threw in the towel. "I don't know how large 'large' is
anymore," he said. But at least there wasn't any doubt about the
Rover navigation system. At 2.4 kilometers out - according to the
navigation system - they began to see details on the LM. Four hours
after they set off for the mountain, they were back at "home,
sweet home", 85 pounds of rocks and soil richer.

If the first part of the EVA made for the sort of geology-rich day
that Dave Scott could really enjoy, the drilling promised to be his
penance. And for Jim Irwin, the cost of the honor of having spotted
the Genesis Rock was a set of soil mechanics experiments that he would
perform while Scott did the drilling. Irwin almost wished that he
could trade jobs; the instructions for the soil mechanics experiments
filled five full pages on the cuff checklists. In comparison, the
tasks for a geology stop usually only filled two pages.

As Scott told Allen: "Before we got out this morning, we figured
you guys had a conspiracy against us, having Jim doing...(the soil
mechanics experiments) and me drilling at the same time."

The soil mechanics experiments were designed to give the engineers
detailed information on the stability and load-bearing characteristics
of the regolith, information that would be useful in planning for an
eventual lunar base. The engineers had, of course, been able to deduce
a good deal of such information from the depth of footprints and Rover
tracks, the depth to which core tubes could be pushed and/or hammered,
and the stability of the walls of trenches dug by the crews of Apollos
12 and 14. Here at the Apollo 15 site, Irwin would supplement those
inferences with quantitative measurements made with an instrument which
recorded the amount of force that he needed to exert to penetrate the
soil with a thin, cone-tipped rod. As it turned out, the soil was
about as hard and compact at any encountered by Apollo crews and that
fact, in hindsight, suggests that Scott was not only fighting a poor
drill stem design, but was also drilling into intrinsically stiff
dirt.

Not surprisingly, NASA's experts had been thinking about the drilling
problems ever since Scott abandoned the effort the night before and now
suggested that he run the drill for a short while without pushing down
on it. Then, if he noticed it starting to bind again, they wanted him
to try raising the stem a little bit to clear the flutes.
Unfortunately, even with Scott just holding the drill as lightly as he
could, it bound up almost immediately and, as well, he found that it
took a great deal of effort to pull the stem up even a short distance.
With the power on, he said "it pulls me right on down with
it." By straining for all he was worth, Scott managed to lift the
assembly a few inches; that seemed to help for a few seconds, but then
the drill bound up again, even tighter than before, like a "steel
vise."

Scott's hands were beginning to give out and it wasn't long before
Houston decided to call it quits again. Perhaps, they all thought,
they'd made a little extra depth. However, when Scott tried to insert
the heat flow probe, it wouldn't go deeper than about 100 centimeters.
What had happened was that, when he lifted the stem part way out of the
hole, the bottom section stayed bound in the hole and separated from
the next one up. And when he started drilling again, the second section
deflected to the side and became firmly wedged against the first
section. In short, Houston's suggestion had only made matters worse.
Fortunately, although the heat-flow experimenters had to take
extraordinary care in interpreting the data from the second hole, they
were eventually satisfied that they were getting good measurements.
The results of the Apollo 15 heat-flow experiment were consistent with
those made on Apollo 17.

After finishing the second heat-flow hole, Scott took a short break to
help Irwin with a trenching experiment. While Irwin dug, Scott took
pictures. Irwin got down to about a one-foot depth, but then had to
stop because the soil was so compact that he was almost sure he'd
reached bedrock. Scott then helped Irwin seal a trench sample in a
vacuum-tight can before getting back to what he facetiously called his
favorite task. There was, after all, still the deep core to be
obtained and Houston wasn't at all sure that the drill's power supply
would last out the rest period between EVA's. It was now or never.

This time, mostly because of a good stem design, the drilling itself
went fairly smoothly and Scott got the six sections of core tube in
their full depth of 2.4 meters after only a few minutes of effort
However, although the core stems would turn in the hole when Scott
pulsed the drill, once again, cuttings filled the flutes enough that he
was unable to pull the core out of the ground. The hole had been
drilled and, presumably, the core tube now held a detailed section of
soil nearly half way down to the top of the lava below; but Scott was
rapidly running out of oxygen and it was time to get back into the LM.
The core tube would have to stay in the ground for a few more hours.
Tomorrow, they would try to pull it out.

Because of the drilling problems and number of tasks new to this
mission, by the end of the second EVA, Scott and Irwin were running an
hour and forty minutes behind the mission timeline. When they climbed
back into the LM at the end of the EVA, they had only twenty-two hours
left before they were scheduled to go back to orbit; and, in that short
period, they still had to complete their post-EVA tasks, get some
sleep, conduct the third EVA, and then, four hours after climbing back
in the LM for the last time, launch and rendezvous with Al Worden.
They were short on time and, because Houston was insisting, sensibly,
on both an on-time liftoff and a full night's rest, the third EVA had
to be shortened. Nonessential activities - like a scheduled science
debriefing - were dropped; but there wasn't much padding in the
schedule. By morning, Scott and Irwin had only been able to catch up
by about ten minutes and were looking at an EVA that would last
"somewhere between four and five hours" rather than the
nominal six. Allen tried to put things in perspective and noted the
highest priority mission goals had already been achieved. With only
slight exaggeration, he said that "we checked off the 100 percent
science-completion square sometime during EVA-1 or maybe even shortly
into EVA-2. From here on out, it's gravy all the way, and we're just
going to play it cool, take it easy, and see some interesting geology.
"It should be", he said, "a most enjoyable day."

Two and a half hours after wake up, Scott and Irwin had finished
breakfast and, as they listened to Houston's plans for the day, were
well into their preparations for the EVA . For the first three hours
they would follow the flight plan and drive west to the rille for
sampling and photography. But, then, they would have to turn for home
without going to a cluster of craters called the North Complex where,
from slim evidence seem in orbital photography, the geologists hoped
that evidence of post-mare volcanic activity might be found.
Inevitable as it was, the deletion of the North Complex stop was
something of a disappointment and Scott asked Houston to hold open the
possibility of at least a quick foray. Joe Allen told him that the
request had been noted. "We copy that, and it may well be that we
can get up there. We'll just see how it goes."

Three hours after wake-up, Scott and Irwin were out on the surface.
They made good time loading their backpacks and the Rover with tools
and sample bags and, just forty-three minutes after depressurization,
they were ready to leave the LM. However, before they could drive to
the rille, there was the not so minor matter of retrieving the deep
core and they could only hope that the bad luck they'd been having with
the drilling had ended.

But it was not to be. The drill stem wouldn't budge - even with both
of them lifting on the drill handles. At Houston's suggestion, they
tried running the drill for a few seconds, but all it did, Scott said -
laughing at the humor of the situation - was that it "sucked me
right back down". There was power left in the battery pack after
all and, Scott described the situation: "What happens, Joe, is
that, when I turn the drill on, the drill drills - like all drills
should."

What they needed was a jack of some sort, a way to gain some
mechanical advantage, but that would have to wait for Apollo 16. For
now, all they had was their own muscles and gradually, by getting
elbows and then shoulders under the drill handles, they pried it up a
few inches at a try. Time and time again they counted off, straining
together on the count of three. Ten minutes into the effort there were
some real signs of hope.

Scott pushed once more with his shoulder; and the core came out.
Unbeknownst to anyone else, he badly sprained his shoulder in the
effort. However, a shoulder would heal faster than a memory of a core
tube left stuck in the lunar surface. They'd gotten the job done, and
that was what mattered. Sore as he was, Scott would be able to get the
rest of the day's work done without any problem. There certainly
wasn't any point in calling the sprain to Houston's attention. Once he
was back in the cabin he would take some aspirin to ease the pain but,
for now, there was a final EVA to complete.

As he and Irwin struggled to remove the core, what Dave Scott wanted
most for Houston to tell him was that the effort was worthwhile. It
would be a while yet before he said anything, but his frustration
showed up occasionally in his tone of voice. For one brief moment
after they'd gotten the core out, he was even a bit abrupt with Houston
when Allen asked Irwin to go ahead and take some pictures of the
trench. Somewhat pointedly and certainly uncharacteristically, he
said, "Joe, just standby until we get this settled down; and then
we'll come at you for what is our next task. You're going to have to
just hold off on jumping ahead of us, because we always have to come
back and ask you what you said anyway."

Allen, who surely ranks as the most diplomatic of all the people who
served as EVA CapComs, backed off immediately. "Read you loud and
clear," he said.

And there the matter might have ended, but for the fact that, despite
having worked superbly as a stand in "wrench" at the end of
EVA-1, the vise on the back of the Rover wouldn't work. The vise was
designed specifically to grip a section of core so that it could be
separated from the other sections. However, as Scott discovered, the
vise would hardly grip at all. By grasping the core tube tightly in
one hand, Scott managed to remove each of the top three sections but
then couldn't separate the bottom three. As he worked, he realized
that the vise was mounted on the Rover backwards, a remarkable
discovery since the mounting hardware ensured that the vise could be
put on only one way. As it turned out, the error originated in an
engineering drawing which hadn't been caught because, during assembly
of the training version of the Rover - either accidentally or for the
obvious reason that the vise wouldn't work as drawn - the mounting
hardware had been installed backward from the drawing. However, that
information wasn't passed on to the people who assembled the flight
Rover, nor was the drawing changed; and, consequently, Scott and Irwin
found themselves with a tool that wouldn't work. Because the lower
sections of the core tube had been turning in the ground longest, they
were stuck together too tightly for Scott, even with Irwin's help, to
separate by hand.

Finally, after Scott and Irwin had spent a half hour on the core,
Houston advised them to lay the remaining sections on the ground and
proceed with the traverse. Irwin noted that the remaining
three-section piece was short enough that they might be able to take it
into the LM as it was, although Scott wondered where it would fit in
the Command Module. Houston had nothing, as yet, to say on the matter
and, indeed, Scott finally decided that it was time to remark on the
amount of time they spent on the core.

'Hey, Joe, you never did tell me that (core) was that important. Just
tell me that it's important, and then I'll feel a lot better."

"It's that important, Dave," Joe Allen said.

"Okay. Good. Because then I don't feel like I wasted so much
time.

"No," said Allen. "Quite seriously, Dave and Jim,
that's undoubtedly the deepest sample out of the Moon for perhaps as
long as the Moon itself has been there."

After the mission, the Apollo 15 core tube was promptly x-rayed and
Scott had the pleasure of showing the pictures at a press conference.
During the drilling, he had penetrated over fifty distinct layers, an
extraordinary record of the multiple events which created this
particular column of soil. Studies of the deep cores obtained on
Apollos 15, 16, and 17 provided details that were critical to an
understanding of the processes that produce the soil layers. When
combined with more qualitative observations about the depth of craters
that bring blocks of bedrock to the surface, these details give some
confidence in predictions of such things as the prevalence of rocks at
depth, a matter of some importance to civil engineers designing buried
or partially buried structures for a lunar base and to mining engineers
interested in processing large quantities of regolith in order to
extract such things as the hydrogen, carbon, and helium-3 implanted by
the solar wind. From this point of view, the extra effort - that
undoubtedly cost Scott and Irwin the chance to visit the North Complex
- was worthwhile. And of course, as the first crew to attempt so
ambitious a mission, it would have been extraordinary if Scott and
Irwin had not run into difficulties at some point. Compared with the
troubles that cost the Apollo 13 crew a landing, the loss of an hour's
worth of time was a relatively minor matter. It would have been nice
to get to the North Complex; but, then, none of the Apollo crews had
time enough on the Moon to do all they could have done with the
equipment at hand. A brief stay dictated compromise.

The series of minor troubles that had been plaguing Apollo 15 hadn't
quite ended yet. With the core out of the ground, Scott's next task
was to mount the Rover and, with Irwin standing by with a movie camera,
put the Rover through its paces for the Boeing and Marshall engineers.
Unfortunately, as Scott drove by for the first time, Irwin found that
the movie camera wasn't working. On his own initiative, Scott decided
that they would abandon the Grand Prix. The engineers would have to
wait for Apollo 16 to get a movie and, for now, it was obvious that the
Rover was working beautifully. Verbal descriptions of it's performance
would have to be enough.

Houston lost no time in supporting Scott's decision.

"That was a good try," Joe Allen said. "Let's press on
to Station 9. Let's take a good, clean, comfortable look at that
rille."

"Yeah, that's a good idea, Joe," said Scott, eager to be
off. "Best idea you've had all morning."

An hour and a half into the EVA, they were finally on their way. Now
that they knew almost exactly where they had landed, they knew that the
drive to the rille would be a quick one: a trip of about two kilometers
that would take ten to fifteen minutes, depending on the sort of
terrain they encountered. During the Standup EVA, Scott had gotten a
pretty good look at the countryside in all directions except the west.
For the same reason that the Apollo 12 crew had been slow to recognize
that Head Crater sat just down-Sun of them, Scott hadn't been able to
see much detail in the direction of the rille and, now that he was
driving toward west, he and Irwin could only assume that they would
find the same sort of terrain that they had found south of the LM.
Consequently, their encounters with a series of three large depressions
came as something of a surprise. On their own scale, the depressions
were shallow - with inner slopes of only about three degrees or so.
However, each of them was up to two hundred feet deep and that was
enough to send Scott on a detour.

The surface, Scott said, "is smooth but rough. Smooth on a small
scale" but rough enough on the large scale that "you really
could get lost. Up and down."

"It's like driving over the big sand dunes in the desert,"
Irwin added. It wasn't at all like driving up to Hadley Delta, he
said. There, "you could always look back and see the LM."

Along the section of the rille that Scott and Irwin were approaching,
the western rim is about 30 meters lower than the eastern rim, and it
was only at high points on the traverse that Scott and Irwin caught
glimpses of the far wall. Ten minutes into the drive, at a point about
half a kilometer short of the near rim, they got a momentary look at
it. And then they saw it again when they got to a brief sampling stop
at a small, fresh, soft-rimmed crater.

Over the last 200 to 300 meters of the approach to the rille, the
surface slopes gently down toward a line of light-grey boulders that
marked an apparent edge and, as Scott and Irwin approached, the number
and size of rocks they saw sticking up through the soil increased
steadily. Long before Apollo 15, a number of clues had suggested to
geologists that Hadley Rille was a lava drainage channel - or drainage
tunnel - left over from the time when the mare were being filled. Or,
perhaps, the Rille had begun its life as a fault, or a series of
faults, running roughly parallel to the western slopes of Hadley Delta
which was then eroded - rather than filled - by the thin, liquid mare
lavas. Whatever the rille's origin, once the flow of lava stopped, the
steady rain of impactors gradually eroded roofs, rims and walls and
slowly filled the bottom of the channel with debris, building up talus
slopes, and moving the edges of the canyon outward. With luck the
talus wouldn't be piled all the way to the rim and, from their perch on
the edge, Scott and Irwin would be able to see, describe, and
photograph layering in the far wall, layering produced by the sequence
of mare-filing, lava flows. Limitations of time and equipment would
prevent them from making the equivalent of a trip down the trails into
the Grand Canyon for a close look at mare history; but at least, it was
hoped, they would be able to see and photograph enough to give the
geologists insight into the history of mare deposition.

Although pictures that Scott and Irwin took toward the south along the
rille suggest that, along much of its length, the talus slopes have
built up nearly to the rims, when they looked across the canyon - a
distance of no more than a kilometer - they could see obvious layering
within the occasional outcrops that had been preserved. In the upper
60 meters of the far wall, they could pick out at least a dozen
distinct layers; and, because of the winding nature of the rille, to
the south they could see suggestions of similar layering in a section
of the near wall.

500 mm looking south from station 9

500 mm of far rille wall, showing layering

[During a review of this Apollo 15 summary, I asked Jack Schmitt why
there were outcrops visible. Was it that the rill wasn't old enough
for the talus to have built up to the rim?

Jack told me, "Those rille walls are working away from the
centerline due to impact. And, because they're steep walls, the debris
has a statistical tendency to go down to the bottom, rather than lying
on the walls. So they are going to maintain exposure, unless hit by an
impact big enough to destroy the whole section of wall. The original
configuration was probably a lava tube. Sometimes lava tubes are open
and sometimes they're roofed over, depending on the dynamics of the
individual flow episode. It's amazing how they tend to maintain
themselves. There's probably melt erosion that helps to maintain them
- and which coats over the walls and hides any layering in the
surrounding rock. But, as soon as all the eruptions stop, impacts
break through any roof that might have been present - which would be
relatively thin - and start to erode the wall cover back. After than
happens, you start to see the exposed layers."

I asked if the persistence of the vertical faces was evidence of
hardness variations, like we see in New Mexico mesas. "That's why
you see the layers. The interior of the flows are probably softer than
the exteriors, because they haven't been quenched (by radiative
cooling). The exteriors tend to be denser and harder, although that
depends on how vesicular they were. So every flow is a different
story. If you look at the Apollo 12 material that seems to have come
from deep down in the flow - and actually some of the Apollo 11 rocks
that I called gabbro to distinguish them by texture from basalt - when
you get coarse crystals, they just tend to be more friable
(breakable)."]

The visit to the rim of Hadley Rille not only provided glimpses into
the structure of the bedrock underlying the landing site, but also a
new perspective on the structure of the regolith. Although the
thickness of the soil layer undoubtedly varies from place to place
around the landing site, evidence from the seismic signals generated by
the astronauts as they walked around the LM/ALSEP area and evidence
from the depth of craters that brought up bedrock fragments suggests
that the regolith is typically about five meters thick. However, as
Scott and Irwin approached the rille, they had seen clear evidence of a
thinning of the soil layer. The thinning was a simple consequence of
the presence of the canyon. Away from the rim, crater ejecta is
scattered in all direction; the crater dug by one impact is gradually
filled with ejecta from later impacts and, except for the effects of
the occasional, larger impacts, the net result is that the average
depth of the layer isn't influenced at all. However, near the rim,
ejecta thrown toward the canyon tumbles onto the talus slope and isn't
replaced by anything being thrown back out. Slowly, the canyon is
filling and, the closer one gets to the rim, the thinner the soil
layer. This thinning produces both a surface that slopes down toward
the rille and an increase in the prevalence of rocks lying on the
surface. Close to the edge, in a strip extending up to 25 meters back
from it, there is hardly any soil at all and the surface is littered
with boulders lying practically on bedrock. And it was bedrock that
they were after.

Because the Rover had only 14 inches of clearance, Scott and Irwin
parked on soil well back from the edge of the rille. Then, once they
finished describing and photographing the far wall, they moved down to
the boulders. Scott was quite confident that these were bedrock
boulders; and Houston was so interested in them that they readily
agreed to drop a more conventional mare sampling site scheduled for the
trip back to the LM in favor of an extension here. Scott and Irwin
took pictures, sampled boulders, raked the soil near the Rover for a
collection of small rocks, bagged soil samples, and drove two short
core tubes into the ground. In all, they collected over a hundred
pieces of rock - all fragments of the bedrock basalt, excepting only
six breccia fragments which were, themselves, made up mostly of bits of
basalt.

The station was both productive and fun. Scott and Irwin had clear
objectives for the site and, because of the value of the station, were
given extra time so that they could work without undue haste. They
didn't have any appreciable slopes to content with, so the work wasn't
physically demanding. And, finally, the site offered enough
interesting detail that they were able to put their geology training to
very good use. It was a fitting climax to the mission and indeed, as
they prepared to drive off, Scott neatly summed up his pleasure and his
buoyant mood. "Man, am I going to miss 1/6th g. This is
neat."

Time was running out. Fifty-five minutes after they stopped, Scott
and Irwin were headed north, going to a spot another 200 meters along
the rim so that Scott could take a second series of photographs for a
stereo view of the far wall. It would be a very short stop - for
photography only. Houston wanted them back at the LM in no more than
45 minutes. Lift-off was only five and a half hours away and there was
a good deal still to be done. Scott understood the situation
perfectly, but was still a bit disappointed. "Okay," he
said. "Shoot! No time to go to the North Complex, huh?"

Allen recognized the question as rhetorical and maintained an
appropriate silence while Scott and Irwin went about the business at
hand. Fourteen minutes after they stopped, they were moving again.
They were still faced with the prospect of separating the bottom
sections of core, but were determined that, somehow, they would get the
entire core home. In the end, Houston decided that there would be room
for the three connected section of core in the Command Module; and that
is the way it was done.

In some ways, Apollo 15 was the last of the engineering flights.
Armstrong and Aldrin proved that a landing could be made, and that a
pair of astronauts could go out on the surface and do useful work.
Conrad and Bean proved that the LM could be flown to a predetermined
target, and that there was no real problem in working for several hours
at a time. Shepard and Mitchell showed that, in the event of a Rover
breakdown, a crew could walk back to the LM from a considerable
distance. And it remained, then, for Scott and Irwin to put the Rover
through it's paces and to demonstrate that the LM, the suits, the
backpacks, and they, themselves, could handle a three-day visit to the
lunar surface.

By the end of Apollo 15, it was clear that, after three very active
days, Scott and Irwin had not exceeded any practical limits to the
length of an Apollo mission. There had been a number of minor problems
with the equipment and, as was further demonstrated on Apollo 16 and
17, an accumulation of small failures was inevitable. Perhaps they
were approaching a limit. At the end of the first EVA, Scott forgot to
stow the small antenna on the top of Irwin's backpack, and it broke off
as he crawled through the hatch. They were able to tape it back on,
but the accident illustrated what could and would happen over time.
Dust was a continual problem and, despite their best effort to clean
each other off at the end of the EVA's, the cabin got dirtier and
dirtier. They put the suit legs in bags to help to control the dust
and, each night, they cleaned and lubricated their zippers and
neckrings and wrist rings. Nonetheless, the closures got balkier with
each passing day. Outside, the dust got into all unsealed moving parts
and, although the 15 crew didn't experience nearly as many dust-related
Rover or tool problems as did the later crews, they accumulated
scratches on their visors and, because the dust covered almost
everything, had trouble reading gauges.

These small problems - and the inevitability that they accumulate -
should serve as warnings for those planning more ambitious missions.
However, in the context of Apollo, Scott and Irwin demonstrated that
three days were manageable and that there was every reason to expect
even greater success from the remaining missions. The drill stems
could be redesigned, the vise could be mounted properly, and other
lessons could and would be learned so that Apollo 16 and 17 would be
even more productive.